Effect of Curing Age on the Microstructure and Hydration Behavior of Oil Well Cement Paste Cured at High Temperature

Abstract

With the extensive increase in exploitation of shale gas/oil, the mechanical/physical properties of oil well cement paste (OWCP) are paid special attention to. The mechanical and physical properties of OWCP is believed to be closely related to its microstructure and hydration behaviors. Both microstructure and hydration behaviors of OWCP cured at high temperature evolve with curing age. Taking advantage of multiple techniques, this study devotes itself to investigating the impact of curing age on the evolution of microstructure and hydration behaviors of OWCP cured at 80°C. The results show that both the capillary pore space and porosity decreased with curing age, while the gel porosity and specific surface area increased with curing age; Ca/Si ratio of calcium silicate hydrate (C─ S─ H) decreased fast during the first 3-day curing age, and then it is maintained around 1.82 in the following curing age; both evolutions of degree of hydration and chemical shrinkage with curing age obey the Avrami-type exponential equation; and the porosity of OWCP measured through mercury intrusion porosimetry correlates linearly with gel/space ratio as does the relationship between the degree of hydration and total amount of portlaindite determined by thermogravimetry-differential thermal analysis (TG-DTA), and both linear relationships are independent of curing temperature.